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This easy Crockpot French onion soup has rich, beefy broth filled with caramelized onions and topped with melty cheese. I love this hands-free spin on the classic recipe, made in the slow cooker!
For more cozy soup inspiration, try this creamy tortellini soup and Italian wedding soup.
I love anything French onion—from French onion soup chicken to French onion pasta—and today’s Crockpot French Onion Soup might just be my favorite way to enjoy this classic! It’s savory and delicious, with plenty of caramelized onions cooked in a rich, beefy broth with herbs. This weeknight-friendly version leaves the work to my slow cooker, and the flavors are incredible after hours in the low and slow heat. All that’s left to do afterwards is add bread or croutons, and melt over the cheese!
Why I Love This Crockpot French Onion Soup
- Rich and savory. This soup gets its flavor from sweet, caramelized slow-cooked onions in a savory beef broth with herbs. Don’t forget the thyme! It’s the perfect pairing with all that buttery richness.
- Cheesy. Just like the classic recipe, I top my bowls with thick slices of crusty bread and heaps of melty Gruyere cheese. Too good!
- Make-ahead. This soup comes together over hours in the crockpot, and most of them are completely hands-free. I love that I can leave it to my slow cooker and come back to a cozy onion soup that’s ready to serve. Or, I’ll freeze it for future cravings!
Ingredients You’ll Need
Most of the flavor in French onion soup comes from the combination of onions caramelized in butter, with a splash of wine and fresh thyme. I’ve included some notes here. Have a scroll to the recipe card after the post for a printable ingredients list with amounts.
- Onions – The best onions for French onion soup are sweet onions, like Vidalia, which aren’t as pungent. You can use yellow onions if that’s what you have. In that case, add an extra 1/4 teaspoon of sugar to the recipe.
- Unsalted Butter – Salted butter works, too, just reduce the added salt that comes later on.
- Sugar – Granulated, brown sugar, or any kind of sugar (except powdered sugar) will work here.
- Seasonings – Fresh thyme is a must! Emphasis on fresh. It’s the signature aromatic for this soup. You’ll also need salt and pepper to taste, and a bay leaf.
- Beef Broth – I use low-sodium beef broth or stock. Chicken broth is a good alternative, though the soup won’t be quite as rich. For a vegetarian version, use vegetable stock.
- White Wine – Choose a dry white wine, like Chardonnay or Pinot Grigio. If you’d prefer to cook without it, substitute extra stock instead.
- Bread – For topping the bowls. You’ll want to use sturdy, crusty bread, like French bread. You can also top your soup with croutons.
- Gruyere cheese – The classic choice for French onion. Feel free to use Swiss cheese, or another melty cheese instead.
Recipe Tips
- Use croutons. Don’t worry if you’re out of French bread, you can top it with your favorite croutons for the same texture.
- Lighten things up. Feel free to skip the bread and cheese if you’re looking for a lighter bowl of soup. The richness will still be there, and the soup still tastes amazing!
- Watch the onions. There’s a fine line between golden, caramelized onions and burnt onions. Keep an eye on the color and remove them from the heat once the onions have caramelized, otherwise, your soup will taste bitter.
Serving Suggestions
This crockpot French onion soup is the perfect “fancy” starter! I love to serve it with my easy rib-eye steak dinner or grilled scallops when we have guests over for dinner. Sometimes, I’ll bulk things up further with couscous and a side of caponata. This cheesy, beefy soup is also a cozy lunch served bistro-style with a Cobb salad.
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Crockpot French Onion Soup
Ingredients
- 6 sweet onions, sliced
- 4 tablespoons unsalted butter, melted
- ¼ teaspoon sugar
- ½ teaspoon salt
- ½ teaspoon fresh ground black pepper
- 4 to 6 sprigs fresh thyme
- 1 bay leaf
- 6 cups low sodium beef broth
- ½ cup dry white wine
- salt and fresh ground black pepper, to taste
- 6 slices french bread, optional
- 1½ cups shredded Gruyere cheese, optional
Instructions
- Caramelize the onions. Place sliced onions in a 6-quart slow cooker. Stir in the melted butter, sugar, salt, and pepper. Top with thyme and bay leaf. Place the lid on the pot and cook on LOW for 8 hours, or until the onions are browned and caramelized. Stir halfway through.
- Make it soupy. Once onions are caramelized, stir in the beef broth and wine. Taste for salt and pepper and season accordingly.
- Cook. Cover and cook on LOW for 4 hours or on HIGH for 2 hours, until heated through.
- Ladle into bowls. Remove the lid and discard the thyme and bay leaf. Ladle the soup into ovenproof bowls and transfer the bowls to a large baking sheet.
- Add toppings. Top the soup in the bowls with a slice of French bread and shredded cheese.
- Melt the cheese. Turn the oven-broiler to High. Broil the soups in the oven until the cheese is melted, about 2 to 3 minutes.
- Serve. Remove from oven and enjoy.
Notes
- For a lighter option, omit the bread and cheese.
- For a quicker version, start the soup on the stovetop. Mix onions, butter, sugar, salt, and pepper in a big skillet. Cook until they’re brown and caramelized, around 25 minutes. Then, shift the onions into the slow cooker, and add beef broth, wine, thyme, salt, and pepper. Let it cook for 6 hours on LOW. When done, pour it into oven-safe bowls, add a baguette slice to each bowl, sprinkle shredded cheese on top, and broil until the cheese melts.
- Keep a close watch on those onions. It’s a narrow line between lovely golden caramelized onions and scorched ones. Once they’re caramelized, pull the pan off the heat to avoid a bitter soup.
- Use croutons: If you’re out of French bread, swap it for your favorite croutons to get that same crunchy bite.
Nutrition
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.
How to Make French Onion Soup in the Slow Cooker
This slow cooker French onion soup comes together in two stages: slow cooking the onions so that they caramelize, and then slow cooking again with wine and stock. You’ll find the printable recipe details in the recipe card below the post.
- To start, dump your sliced onions into the crockpot with melted butter and sugar, and let that cook, covered, for 8 hours on LOW. You want the onions to be nicely browned and caramelized before you add the stock.
- Stir in the beef broth, wine, thyme, and bay leaf, and cook for another 4 hours.
How to Serve
When you’re ready to serve, ladle your slow cooker French onion soup into bowls. Top each bowl with a bread slice and load on the shredded cheese. You’ll pop that under the broiler for 2-3 minutes to get the cheese golden and melty. I like to place the bowls onto a baking sheet first. It makes it easy to transfer them to and from the oven!
Speed Things Up On the Stovetop!
If I’m pressed for time, I’ll kickstart this soup by caramelizing the onions on the stovetop first. All you do is combine the onions, butter, sugar, salt, and pepper in a large skillet, and let that cook for about 25 minutes. Add the browned onions to the slow cooker with the stock and herbs, and proceed with the recipe, cooking on LOW for 6 hours instead.
Storing and Reheating Leftovers
- Refrigerate. This onion soup only gets better with time! Refrigerate the soup in an airtight container for up to 4 days. The flavors continue to mingle and the leftovers are delicious.
- Reheat. Microwave servings for 1-2 minutes, or until warm. You can also reheat this soup in a pot on the stovetop over medium heat for 5-7 minutes.
- Freeze. French onion soup freezes great. Transfer soup portions to freezer-friendly bags or containers and freeze the soup for up to 3 months. Let it thaw in the fridge overnight before serving. Reheat it as usual.
I made this soup it was very good however how many cups of onions would you say are the 6 onions it seeemd like a lot of onions
Hi there! I’m so glad you enjoyed the soup! 😊 As for the onions, it can definitely seem like a lot at first, but they cook down quite a bit as they caramelize. For reference, 6 onions usually yield about 6 to 8 cups of sliced onions, depending on their size. If you ever want to adjust the amount, feel free to start with fewer onions and see how it works for you—it’s a pretty flexible recipe. Thanks for trying it out!
This was so good! I threw in some leftover pulled pork that I needed to use up. So good! It would have been good without it too! Thanks for the recipe!
I am very glad you enjoyed it! Thank YOU! 🙂
Love how easy this is to make in the slow cooker! Such a hearty and filling comfort food dinner for the family!
I made this using my own stock it is delicious !!!